Tandy 128K Color Computer RGB Cable

Almost obsessively I try to ensure that I can get the best output from all of my micro computers & consoles. More often than not this involves an RGB connection.

The CoCo3 has an RGB output via a connector, although some effort is required to use it.


As indicated, the RGB port is located underneath the CoCo 3 and uses an IDC 10 pin connector. These connectors can be bought very cheaply on eBay, with 2 connectors attached to ribbon cable. I think mine was $1.49 shipped.


Imagine the computer sitting normally. The pin out assignment is marked as above in the picture (click the picture for a larger view).

The pin out is as follows:

1 – Ground
2 – Ground
3 – Red
4 – Green
5 – Blue
6 – Key (not used)
7 – Audio
8 – HSYNC (Horizontal)
9 – VSYNC (Vertical)
10 – Not used

Make sure if you refer to the picture above for the pin out, to take into account the order/ position of the pins looking from underneath at the RGB socket.

The first thing to note is that there is no composite sync output. It is possible to make an adapter to extract c sync, but I thought I would try with one of my many RGB monitors without needing this.

I did find that I could not manage to get the CoCo3 to sync with a Commodore 1084-P or a 1084SP-1 monitor. However it did sync with an Atari SC1435 minitor, so I will describe the process below.



Here is the IDC connector to use. I cut mine down in the middle.


Separate each strand by about 2cm in length, strip and tin the ends.

The pin out for an Atari SC1435 monitor is as follows:


Source: http://www.gamesx.com/avpinouts/sc1435.htm 


I made a short connector with the ribbon cable, soldering a male DB9 connector with the Atari SC1435. Then made a cable with DB9 connectors going straight through to get to the monitor.



So the photo is not so good, but the RGB output is very crisp and clean.


Leave a Reply

Your email address will not be published. Required fields are marked *